The control of disposable airborne waste such as wood dust and other airborne waste having fine particulate in its make-up from industrial sites has been accomplished in the past usually by moving exhaust air through filter means such as cloth tube filters and wet collectors and by centrifugal separation of the particulate from exhaust air. The filter system for dust collection is an effective method for dust collection, but by comparison to other methods the typical filtration system is very expensive to construct, and in the operation of a filtration system increased static pressure losses of the exhaust air occur and therefore increased fan horsepower is required to force the exhaust air through the filter media, resulting in more expensive power requirements to operate the system. The conventional centrifugal separation systems are not as effective as filter systems but they are much less expensive to construct and to maintain. While the centrifugal separators are less expensive to purchase and to operate, some pollution standards are not met by many of the conventional centrifugal separators. If the centrifugal separator in an operating plant must be replaced by a new, more efficient centrifugal separator or by a filtration system to meet the pollution standards, the fan, ductwork, supports and other elements supporting the old separator usually must be replaced and the owner of the plant may be faced with substantial equipment purchase costs and installment costs, as well as temporary plant shutdown.
While the prior art has suggested injecting fluid into a particulate laden air stream to improve the collection efficiency of a centrifugal separator, the fluid injection was not precisely controlled so that an improper amount of fluid could be injected into the gas stream. Too little fluid results in poor collection efficiency, and excessive fluid results in the particles becoming excessively moisture laden and wet. The resulting waste product is difficult to handle in further processing and in disposal. For example, in the field of wood waste, excessive moisture tends to cause plugging in the cyclone separator, to cause difficulty in physically handling its disposal, and when combustible waste is used as boiler fuel, excessive moisture causes inefficient combustion and other operation problems in some boiler designs.
The recycling of waste has become more prevalent and waste is transported long distances for subsequent processing in other products. Any increase in moisture content results in increased weight and increased freight costs, and such increased moisture content in many cases can result in the waste product being unusable or difficult to use.